How to Strip the Zinc Plating From Bolts

The shine on new bolts comes from zinc plating.

To protect bolts from rust, manufacturers add zinc plating. This coating is shiny and may stand out on construction projects that are attempting to re-create an aged or rustic appearance. Removing zinc plating requires the use of hydrochloric acid, which can be purchased as muriatic acid --- a highly corrosive agent that reacts readily with the zinc plating. Before purchasing muriatic acid, contact your local water company or hazardous waste disposal company for proper solution disposal procedures. A working muriatic acid solution should be a 1:10 dilution of acid to water.

Things You'll Need

• Muriatic acid
• Zinc-plated bolts
• 5 gallon bucket
• 3 gallon bucket
• Water
• Glass measuring cup, Pyrex if available
• Mask
• Gloves
• Goggles or other protective eyewear
• 1 pound sodium bicarbonate (baking soda)
• Steel tongs

Instructions

Stripping Zinc Plating with a Muriatic Acid Solution

1. Calculate the ratio of muriatic acid to water. A gallon of liquid equals 16 cups. For a gallon solution of 1:10 ratio of muriatic acid to water you need 1.6 cups of muriatic acid and 14.4 cups of water. Do not mix more than a gallon of solution at a time. The greater the volume of the solution, the harder it will be to neutralize later.

2. Place all of your materials in a well-ventilated area, preferably outside.

3. Put on protective gloves, mask and eyewear before preparing the solution.

4. Add the water to a 3 gallon bucket.

5. Add the muriatic acid to the bucket. Always add acid to water. Adding water into acid creates an exothermic reaction that will produce enough heat to melt the bucket.

6. Use the steel tongs to carefully place the zinc bolts into the solution. The bolts will fizz in contact with the solution, releasing hydrogen gas.

Neutralizing the Bolts and Muriatic Acid Solution

1. Fill the 5 gallon bucket half full with water. The amount does not have to be exact.

2. Add baking soda to the water while stirring. Add enough baking soda that a thin film of precipitate remains on the bottom.

3. Use the steel tongs to remove the bolts from the bucket and place them in the neutralization solution.

4. Allow the zinc-plated bolts to sit for two to three minutes or until any noticeable chemical reaction has ceased.

5. Remove the bolts from the neutralization bucket and flush with a garden hose or under a faucet for at least five minutes to remove all traces of muriatic acid.

6. Pour the muriatic solution into the neutralization bucket slowly. Be careful not to splash the solution on clothing or exposed skin.

7. Add additional sodium bicarbonate to the neutralization solution if it continues to fizz.

Tips & Warnings

• Use only industrial grade plastic buckets. Do not use household mop buckets since the plastic will be too thin and may react with the muriatic acid.

• Exercise extreme caution when using muriatic acid.

• Do not dump excess muriatic acid or the neutralization solution into local water supplies or your yard without authorization.

References

• All Things Concrete: Acid Cleaning Concrete with Muriatic Acid
• CalculateMe: Convert Gallons to Cups
• Massachusetts Department of Environmental Protections: Muriatic (Hydrochloric) Acid
• N.C. Department of Health and Human Services Hazardous Substances Emergency Events Surveillance Program: Hydrochloric Acid Facts
• SmokStak: Removing Zinc Plating
• Practical Machinist: Removing Zinc Plating

Resources

• Brown University: Material Safety Data Sheet Muriatic Acid